Description (adapted from the application): This pilot project deals with elucidation of mechanisms involved in the DNA/lipid complex-induced toxicity in CF patient during cationic liposome-mediated gene therapy. The symptoms observed include fever, myalgia and arthralgia, occurring at six hours with full recovery between 24-48 hours after the administration of DNA/lipid 67 complexes. The applicant believes that the toxic effects of DNA/lipid complexes are caused by unmethylated CpG motif in plasmid DNA. It is hypothesized that CpG motif activates T lymphocytes and macrophages to release inflammatory cytokines (TNF-a and IL-1), Th1-inducing cytokines (IL-12 and IL-18), Th-1 cytokine (IFN-r), leading to fever, myalgia, arthralgia and activation of NK and B cells. The applicant has proposed two Specific Aims to test his hypothesis. Aim 1 is to explore the effect of methylated and unmethylated CpG motifs of plasmid DNA in the presence or absence of lipid 67 on the production of specific cytokines in human peripheral blood cells (PBMCs) in vitro, and to test the effect of anti-inflammatory cytokines IL-10 and IL-4 on the production of the specific cytokines. Aim 2 deals with similar experiments in vivo using IL-12 or IFN-r knock out mice.